BACKGROUND: Antifibrinolytics such as aprotinin and tranexamic acid have been administered to reduce blood loss of cardiac surgery, but opinions differ regarding the efficacy of each drug. This study was performed to compare the hemostatic effects between aprotinin and tranexamic acid on adult open heart anesthesia and to evaluate their additive effects. METHODS: We randomly allocated 73 patients undergoing coronary artery bypass grafting or double valve surgery to 4 groups. Group I was non-medicated control(n=15), group II(n=21)patients were recipients of a high dose of aprotinin, group III(n=16) patients were recipients of a conventional dose of tranexamic acid, and group IV(n=21) were recipient of both drugs. Cardiopulmonary bypass time, total operation time, hematocrit, platelet count, transfusion amount and 6 hours of postoperative chest tube drainage were measured. RESULTS: The medicated three groups significantly demonstrated less amounts of blood transfusion and blood loss over the first 6 hours at ICU compared to the nonmedicated control group. Total operation times were shorter in group II, III, and IV compared to group I. Use of both agents together was more effective in reducing the total operation time and blood loss compared to tranexamic alone. CONCLUSIONS: We conclude that the use of aprotinin and tranexamic acid result in significant positive hemostatic effects but superiority of one agent vs. the others is not proved. Use of two agents together yield a more positive effective in reducing the operation time and the blood loss compared to single agent alone but further study would be needed to fully confirm.